The present invention relates to a cylinder head for an internal combustion engine adapted to cool a fuel injection nozzle and an area located in the vicinity of suction valve seats and exhaust valve seats thereof.
In a conventional automotive water cooling system the cooling water is recirculated within a water jacket. The water absorbs heat generated by the internal combustion engine to prevent problems which might otherwise be created by thermal load. The cylinder head for such an internal combustion engine includes a fuel injection nozzle, suction valve seats and exhaust valve seats. The cylinder head is formed with a water jacket which surround the fuel injection nozzle, the suction valve seats and the exhaust valve seats and cools them by the cooling water circulating through the water jacket.
FIG. 1 is a cross sectional view of a conventional cylinder head 1 having a water jacket which includes cooling water passages. FIG. 1 particularly illustrates a 2-valve cylinder head for a diesel engine having one suction valve and one exhaust valve per cylinder.
The 2-valve cylinder head 1 is provided with a cooling nozzle director or cooling water passage 2 which serves as a means for injecting cooling water into the water jacket of the cylinder head 1. A foremost end of the cooling nozzle director or cooling water passage 2 is oriented toward a center P of a fitting hole 3 which fits or connects a fuel injection nozzle to the cylinder head 1. The cooling water injected through the foremost end of the cooling nozzle director 2 (identified by a directional arrow in the drawing) flows through an area defined between an outer wall 4 for a suction hole through which a stem of the suction valve (not shown) is inserted and an outer wall 5 for an exhaust hole through which a stem of the exhaust valve (also not shown) is inserted. Thereafter the cooling water flows toward the center P of the nozzle fitting hole 3 whereby a fuel injection nozzle therein (not shown) and an area in the vicinity of the suction and exhaust valve seats are cooled by the concentrated application of the cooling water.
FIG. 2 is a cross sectional view of another conventional cylinder head 10 which includes a water jacket with cooling water passages therein. FIG. 2 illustrates a 4-valve cylinder head which includes two suction valves and two exhaust valves per cylinder.
The 4-valve cylinder head 10 is provided with a bridge portion a located between an outer wall 11 for a suction hole and an outer wall 12 for an exhaust hole. A bridge portion b is located between the adjacent outer walls 12 and 13 for the exhaust holes. A bridge portion c located between the outer wall 13 for the exhaust hole and an outer wall 14 for a suction hole. The bridge portions a, b and c are located outside both the suction and exhaust valve seats and have respective cooling water passages 15, 16 and 17 formed therein. Foremost ends of the cooling water passages 15, 16 and 17 are oriented toward a center P of a fuel injection nozzle fitting hole 18. Cooling water injected through the cooling water passages 15, 16 and 17 (unnumbered directional arrows in the drawing) is concentrated at and cools the fuel injection nozzle and an area in the vicinity of the suction valve seats and the exhaust valve seats.
In order to meet recent requirements for running engines at higher speeds and supercharging at a higher rate, many internal combustion engines, both gasoline engines and diesel engines, are designed to have relatively large diameter suction valves and exhaust valves. Alternately, such internal combustion engines employ four valves per cylinder, namely, two suction valves and two exhaust valves per cylinder. With respect to the conventional 2-valve internal combustion engine, the suction and exhaust valves also have enlarged diameters and a distance L (FIG. 1) between the outer wall 4 for the suction port and the outer wall 5 for the exhaust port is decreased. This decrease in distance presents a sufficient amount of water injected through the cooling nozzle director 2 to flow through the space defined between the walls 4, 5 and thus prevents desirable reduced cooling. This obviously prevents the internal combustion engine from obtaining increased output.
In the case of conventional 4-valve type internal combustion engines, cooling water injected through the cooling passages 15, 16 and 17 toward the center P of the fuel injection nozzle insert hole 18 (identified by directional arrows in the drawing) collides against the outer wall 19 for the fuel injection nozzle fitting hole 18. After colliding against the outer wall 19, the cooling water bifurcates and collides against the stream of cooling water injected from the opposite side, as shown in Figure 2, and this results in cooling water stagnation. Further, as a result of the collision just mentioned, bubbles adhere to the outer wall 19 causing cooling efficiency to be reduced. Accordingly, if an increased output from the 4-valve internal combustion engine is required, thermal load is increased which leads to cylinder head cracking. Consequently, the conventional 4-valve internal combustion engine has a problem in that a highly incrased output therefrom cannot be obtained in the same manner as that of the conventional 2-valve internal combustion engine.